Sietse Ringers authored Jul 15, 2021 and Ivar Derksen committed Jul 15, 2021

This solves the following. If:
- an issuer exists in the scheme whose identifier is of the form $scheme.$issuer$suffix,
  where $scheme.$issuer is another existing issuer in the scheme,
- issuer $scheme.$issuer$suffix has a private key installed in the --privkeys folder,

Then the IRMA server refused to startup with an incorrect error message
("Private key 0 of issuer $scheme.$issuer does not belong to corresponding public key").